This thread has been moved to an appropriate forum...
As per this advice: Who Should Post in Ask a Question? WC members are free to post in all areas of the board. Please use Ask a Question only for time critical help issues that affect the immediate functionality of your device.

It isn't really a technical limitation of Windows, it is just a free market decision. Android alone is reported to be somewhere between 70-80% of the worldwide marketshare of smartphones. iOS makes up nearly all of the remainder. If a developer writes for those two platforms, they can reach nearly everyone who would use their app.

It's not that Microsoft is unable to develop, it's more than as a company they have decided that Windows 10 Mobile is a lot less important. MS, like any company, is all about making money and someone decided it was no longer worth it.

And since Windows on phones has been neglected, developers don't see the benefit for developing for it.

Also, I believe Windows Insider is meant to be both a cost-saving measure and something for the fans. They let go a large number of QA testers (not all, mind you) and it's likely they meant for Windows Insider to be a source of free testing while also letting people who want to try new stuff sooner, try it sooner.

Also Android does do developer previews and iOS does release beta's so yes, the other two do similar, if simpler, things.

It's not a matter of Microsoft being a bad developer. They're one of the most successful and influential software developers in the world. It's more a matter of Microsoft, as a company, failing to appeal to the masses by repeatedly shooting for a goal and simply missing their target. It's a combination of missed deadlines, a critical failure to communicate, a subpar marketing campaign, and the tendency to give up on products before they're ready for prime time. Every company has had its mishaps, but Microsoft's efforts in the mobile smartphone world show just how crucial it is for a modern company to be able to move quickly, openly, and confidently. Microsoft is making steps to rectify these flaws that are hindering it from becoming the next "Apple" but the past mistakes will never go away.

Because of the culmination of these mistakes in the past, Android and iOS now dominate our new mobile-first world, and consequently third-party developers tend to overlook the underused Windows Mobile operating system and focus primarily on exactly where both the money and the users are: Android and iOS. Going hand-in-hand with this is the stigma that surrounds Windows on PC's. People don't think of apps when they think of PC's. They don't think of sleek, ultra-portable laptops and tablets that operate a new, smooth, beautiful, and modern Windows OS, but rather of big, clunky laptops and desktops and either the antiquated designs of Windows past or the almost nightmare-inducing (for some reason) Metro UI of Windows 8. Because of this, Windows is left behind.

Now, we can't forget all the steps Microsoft is taking to dig itself out of this hole, such as the prospect of a unified operating system that moves seamlessly from device to device with a single Store, a single design language, and a single foundation on which it all operates. Does this guarantee the future of the mobile market for Microsoft? Absolutely not. But it definitely puts them in a pretty great place. For the first time in years Microsoft and their OEM's have started reversing the falling tide of PC sales, while Apple's iPads continue to plummet. The Surface business is now a billion dollar department. And where once Apple was the innovator, now HP, Dell, Microsoft, and other OEM's continuously take age-old ideas and reinvent them for our technological world.

And about the Windows Insider program. That is not a program for the every day consumer. Microsoft does not encourage everyone to join and test technical previews of the Windows operating system. It is for IT professionals, for Windows enthusiasts, for developers. It is for the people willing to put their secondary and tertiary devices at risk for the sake of testing unreleased builds of Windows 10 in order to help Microsoft refine and improve it. The Windows Insider program is the perfect example of what attitude Microsoft should bring to the rest of its company: communication and community. It is not entirely unique, as Google and Apple both have beta and developer preview programs, but neither one of those companies go as far as Microsoft or let people see such early code.

Finally, as far as Windows 10 Mobile goes, it's been working fantastic for me. It has taken far longer to get to the stability it is at now, but I thoroughly enjoy using it as my every day mobile operating system. It's beautiful, secure, and runs smoothly. I cannot claim that it is the same for everyone though.